Modern offices, for example, may consume large amounts of electricity for operating equipment such as desktop computers, word processors, calculators, electric pencil sharpeners, facsimile machines, sound systems, coffee makers and the like. Various techniques are used for distributing electrical power in an office. For example, several duplex outlets may be hard wired in a single circuit to a circuit breaker. However, there is a relatively low limit on the number of outlets which can be connected in each circuit. Today's electrical code limits a circuit to 13 single and duplex outlets. For many newer installations, modular components are now being used to simplify the installation of wiring. These components include duplex outlets connected through flexible cables to connectors which are plugged into a power distribution box.
In some offices, prefabricated wall panels are used to define separate office spaces. The prefabricated wall panels may be permanently installed or may be movable partitions and frequently include factory installed electrical outlets or a power distribution track. channel or raceway which supplies power to individual or duplex outlets. In some cases, several electrical circuits are carried by a channel to which outlets are attached either at fixed locations or at random locations. Such an arrangement is shown, for example, in U.S. Pat. No. 4,688,869. Different single and duplex outlet configurations are manufactured for electrically engaging different circuits when attached to the channel. Duplex outlets have been designed so that the two individual receptacles connect either to the same circuit or to two different circuits to distribute the electrical load. When four separate circuits are provided in a power distribution channel, ten different split duplex outlet combinations have been required to allow for the different possible combinations of connections of the two receptacles in a duplex outlet to the four circuits. Specifically, if the four circuits are designated I, II, III and IIII, the circuit connection options for the split duplex outlets are: I-I, II-II, III-III, IIII-IIII, I-II, I-III, I-IIII, II-III, II-IIII, and III-IIII. These combinations, in removable receptacle modules, have been necessary to enable user access to circuits while electricians attempted to balance neutral loads. There is a risk with this type of system that the loads will not be equally distributed between the four circuits and that shared neutral conductors will be forced to carry the imbalance between the circuits. Further, there is a risk that electrical noise producing loads will be placed in the same circuit as electrical noise sensitive loads. Circuit connection options are further confused by the choice of two neutrals and two grounds.
In order to handle power requirements in offices, single or three phase power is sometimes used in wall panels to provide preferably four separate single phase circuits commonly via multiwire branch circuits. In the single phase case, the neutral terminal typically corresponds to the center tap on the secondary of a step-down transformer. There are two 120 volt circuits 180 degrees out of phase and the net current flow in the neutral remains low so long as the loads on the two circuits remain fairly well balanced. The three phase power includes a single neutral terminal and three individual terminals which form three separate single phase circuits with the neutral. Typically, 12 gauge wire is connected to the three terminals. Because three balanced load circuits are 120 degrees out of phase from each other, a 12 gauge neutral wire will be adequate if the loads on the three circuits are nearly balanced. However, an unusual imbalance from one circuit can be caused by electronic equipment such as desktop computers. The imbalance can alter raw power and place non-synchronized loads on the shared neutral wire. When the loads from the different phases harmonize, harmonic imbalance can overload the neutral wire. Consequently, a single "super" neutral wire of an oversized 10 gauge wire is now commonly used to supply the three circuits in an office to carry overloads in the neutral wire. The use of duplex outlets connected to different circuits did not eliminate the need for a super neutral because the single neutral is shared by all three circuits.